Relationship expert Steve Ward explains why Ashton may be acting out — and advises Demi what to do if she suspects Ashton is cheating!

Ashton Kutcher, 33, is 15 years younger than his wife Demi Moore, 48 — and it’s their massive age gap that may have lead him to allegedly sleep with 23-year-old Sara Leal. Ashton could be seeking validation from younger women, master matchmaker Steve Ward, host of VH1’s Tough Love, tells HollywoodLife.com exclusively. He may even want to start a family of his own!

“The fact that Demi is significantly older than Ashton only contributes to his propensity to or desire to want to get validation from younger women,” explains Steve. “My guess is that they [Ashton and Demi] tried having a family together. The tried having children. Her children are Bruce Willis‘ children. They are not his children. I think he really wants to start a family himself and that’s probably what lead him to act out.”

Steve can see why a girl like Sara might be appealing to Ashton. She has “nice perky fake boobs,” says Steve. “Kind of looks like an extortionist.”

But cheating isn’t the right way for Ashton to end his marriage.

“There is a right way to end a relationship and being unfaithful is just your way of getting caught,” reveals Steve. “It’s a cowardly way to end a relationship because what you’re hoping is that the person is going to end it for you. That way, it makes it a lot easier to move on if you’re not the one walking away.”

Steve also finds it odd that Ashton and Demi weren’t together on their Sept. 24 wedding anniversary — the day he allegedly cheated with Sara in San Diego while Demi was in NYC. “If they were having a healthy marriage, he could have very easily chartered a jet and gone to New York and been there for her,” shares Steve.

Steve’s best advice to Demi: “If she’s determined that he has cheated on her, for self-respect alone, she needs to divorce him and move on.”